Refining chamber made of platinum group metal materials

ABSTRACT

In some embodiments, the invention provides a refining chamber for glass production, made of platinum group metal materials, with improved refining effectiveness. The refining chamber according has the shape of a tube with a cross section ( 1 ), with the cross section of the tube being shaped, in at least one segment, so that in the operating position the length ( 10 ) of a horizontal line ( 12 ) which divides the surface of the cross section into essentially a lower and an upper segment of the surface, both of which have essentially the same area, is greater than twice the maximum vertical extent ( 30 ) of the lower segment of the surface. The cross section of the refining chamber can, for example, have the shape of an oval, an ellipse, a slot, a rounded triangle or a polygon, and the stiffness of the shape of the refining chamber can be increased by forming radially peripheral creases, corners, waves or folds.

FIELD OF THE INVENTION

The invention concerns a refining chamber made from platinum group metalmaterials, particularly a refining chamber which increases theeffectiveness of refining in glass production.

BACKGROUND OF THE INVENTION

Plant components and parts of noble metals, preferably platinum groupmetal (PGM) materials, are used in the glass industry, especially inplants for fusing and hot-molding special glass.

Platinum Group Metal (PGM) materials are distinguished by their highmelting points, by high temperature resistance, and also by highmechanical strength and resistance to abrasion. Therefore they areparticularly suitable for making structural parts in plants or parts ofplants that come into contact with glass melt. Such suitable materialsinclude platinum and alloys of platinum and/or other platinum groupmetals, which may optionally also contain lesser proportions of basemetals as further alloying components, or oxide additives. Typicalmaterials are refined platinum, PtRh10 (a platinum-rhodium alloycontaining 10% rhodium) or platinum that contains a small proportion offinely divided refractory metal oxide, such as zirconium oxide inparticular, to increase strength and increase resistance tohigh-temperature creep (“FKS (fine-grain-stabilized)” platinum). Thesame or similar materials are also abbreviated as ODS (oxiale dispersionstrength), DPH or ZGS materials. DE-A 2002 886 discloses a possiblemethod to manufacture such materials and its contents and is herewithincorporated by reference. Melt technology plant components, such asthose described above, are used for melting, refining, transporting,homogenizing, and measuring out molten glass.

Melt technology plant components are usually made essentially of platesof noble metal, often as thin-walled tube systems. Molten glass flowsthrough them at temperatures between 1000° C. and 1700° C. These tubesystems are generally surrounded by ceramic, which both insulates andsupports them and which, in turn, is often held by supportive metalstructures such as metal boxes.

The PGM parts are made at room temperature and installed in thecorresponding plants. They are operated at temperatures in the range ofabout 1000° C. to 1700° C.

One process step in glass melting is “refining.” “Refining” involvescomplete dissolution and homogeneous distribution of all the individualcomponents of glass, particularly the elimination of streaks, andrefining, i.e., removal of gas bubbles from the melt. Attaining maximumhomogeneity and freedom from bubbles requires thorough mixing anddegassing of the glass.

For certain special glasses, optical glasses, or even display glasses,refining is done in a PGM tube with a round cross-section. In operation,the tube lies essentially horizontally. The tube is filled half to twothirds full of glass so as to get the best use of the refining chamber,which is made of very expensive material.

The following points, among others, are critical for refining: (a) thesize of the open surface of the glass has a substantial effect on theeffectiveness of degassing; (b) the maximum path of the rising gasbubbles affects the time required for refining; (c) the mixing andthroughput are determined by the flow profile and the velocity of theglass flow; and (d) the temperature of the glass and the temperaturedistribution in the glass affect the refining. As the refining is doneat the highest temperature in the entire glass fusion process, heat isadded directly or indirectly to the refining segment.

There is a need for new and improved solutions for melting and hotforming of glass.

SUMMARY OF THE INVENTION

One aspect of the present invention is to provide new or improvedsolutions for plant components made of PGM materials for melting and hotforming of glass. The invention is particularly based on the objectiveof providing an improved refining chamber and a refining processsuitable for increasing the effectiveness of refining in glassproduction.

In one embodiment, the invention comprises a refining chamber made ofPGM material for glass production, comprising: a chamber in the shape ofa tube having a cross section, wherein the refining chamber comprises atleast one segment shaped so that in when the tube is in operatingposition, a horizontal line, that divides the cross section into anupper section and a lower section is greater than twice the maximumvertical extent of the lower section.

In another embodiment, the invention comprises a process for refiningglass in which the molten glass flows through a tubular refining chamberaccording to the invention, comprising: allowing glass in the moltenstate at a temperature of 1000° C. to 1700° C. flow through the refiningchamber, wherein the cross section of the refining chamber is, in atleast one segment, shaped so that in the operating position the lengthof a horizontal line that divides the surface of the cross section intoa lower and an upper section of the surface, both of which haveessentially the same area, is greater than twice the maximum verticalextent of the lower segment of the surface, and/or the level of themolten glass is adjusted so that the surface of the glass perpendicularto the direction of flow of the molten glass has a width which is morethan twice as great as the maximum vertical extent of the molten glassin the refining chamber.

In another embodiment, the invention comprises a process for producing arefining chamber according to the invention, comprising: (a) inserting asmooth-walled tubular segment having two axial ends into a cylindricalmold having an inside diameter and an outside diameter, wherein thetubular segment has an inside diameter and an outside diameter, andwherein the inside diameter is essentially the same as the outsidediameter, and wherein the tubular segment has corrugation-like radialdepressions; (b) providing each of the axial ends of the tubular segmentwith a compression tool that closes the end of the tube tightly, forminga space; (c) filling the space so formed completely with a hydraulicliquid; and (d) generating an internal hydraulic pressure by exerting anaxial compression through the compression tools in such a manner thatthe walls of the tubular segment are corrugated to match the depressionsin the mold with simultaneous shortening of the tubular segment.

In another embodiment, the invention comprises using a tube or a processaccording to the invention to refine glass.

A refining chamber for glass production according to the invention ismade of PGM materials, preferably of FKS 16 Pt alloy. The refiningchamber can be made in the form of a tube with a cross section which isshaped, in at least one segment, such that in the operating position thelength of a horizontal line which divides the surface of the crosssection essentially into an upper and a lower section of the surface,both having essentially the same area, is greater than twice the maximumvertical extent of the lower surface section. The ratio of the length ofthe horizontal line to the maximum vertical extent of the lower surfacesection is preferably from 2.5:1 to 5:1, especially preferably between3:1 and 4:1. In one preferred embodiment, the refining chamber accordingto the invention has the form of an oval, an ellipse, a slot, a roundedtriangle, or a polygon, in which case the design can, according to theinvention, be stabilized by stiffening measures in the shape, such as byshaping of creases, corners, waves or folds.

More preferably the refining chamber has a wall thickness ofapproximately 0.5 mm to 3.0 mm and even more preferably of 0.7 mm to 1.5mm.

Special shaping of the cross section of the refining chamber results inthe following differences and advantages as compared with a knownrefining chamber with circular cross section: (a) the free surface ofthe glass increases, resulting in better degassing; (b) the longest pathfrom the lowest point at the bottom to the surface decreases, whichmeans that degassing requires less time, with the result that either thethroughput increases, the refining segment is shortened, or the crosssection can be reduced. That, in turn, results in less PGM materialsbeing tied up in the production plant, so that costs can be reducedsubstantially; (c) the reduced depth of the glass bath and the alteredflow cross section will result in a different flow profile, which againresults in better mixing of the glass bath; and (d) as heat is addedalong the refining segment, a lesser depth of the glass bath furtherresults in decreased temperature differences in the glass, or fasterheating of the glass.

In summary, the altered geometry of the cross section of the refiningchamber produces better and more effective refining of the glass. Arefining process according to the invention has correspondingly beendesigned according to what has been stated above.

For a better understanding of the present invention together with otherand further advantages and embodiments, reference is made to thefollowing description, the scope of the which is set forth in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiments of the invention have been chosen for purposesof illustration and description but are not intended to restrict thescope of the invention in any way. The preferred embodiments of certainaspects of the invention are shown in the accompanying figure, wherein:

FIGS. 1(a) and (b) each show schematically the cross section of arefining chamber according to the invention in its operating position.

FIGS. 2(a)-(d) show other possible cross section geometries for arefining chamber according to the invention.

FIG. 3 shows a comparison between a round and an elliptical crosssection, each having the same circumference, with the same glassfilling.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described in connection with preferredembodiments. These embodiments are presented to aid in an understandingof the present invention and are not intended to, and should not beconstrued, to limit the invention in any way. All alternatives,modifications and equivalents that may become obvious to those ofordinary skill upon reading the disclosure are included within the scopeof the present invention.

This disclosure is not a primer on refining glass; basic concepts knownto those skilled in the art have not been set forth in detail.

In one embodiment, the invention comprises a refining chamber made ofPGM material for glass production, comprising: a chamber in the shape ofa tube having a cross section 1, wherein the refining chamber comprisesat least one segment shaped so that in when the tube is in operatingposition, a horizontal line 11, having a length 10, that divides thecross section into an upper section 21 and a lower 20 section is greaterthan twice the maximum vertical extent 30 of the lower section 20.

In another embodiment, the refining chamber can be stiffened by shapingmeasures, said shaping measures comprising forming of creases, corners,waves, folds, or combinations thereof, at the circumference of therefining chamber. This particularly applies when the wall thickness isapproximately 0.5 mm to 3 mm and more preferably 0.7 mm to 1.5 mm.

In another embodiment, the refining chamber is configured so that theratio of the length 10 of the horizontal line 11 to the maximum verticalextent 30 of the lower segment of the surface 20 is between 2.5:1 and5:1, preferably between 3:1 and 4:1.

In another embodiment, the refining chamber has at least one crosssection that exists in the tube that is in the shape of an ellipse.

In another embodiment, the refining chamber has at least one crosssection 1 in the tube that is in the shape of an oval, a slot, a roundedtriangle, a polygon, or combinations thereof.

In another embodiment, the invention comprises a process for refiningglass in which the molten glass flows through a tubular refining chamberaccording to the invention, comprising: allowing glass in the moltenstate at a temperature of 1000° C. to 1700° C. flow through the refiningchamber, wherein the cross section of the refining chamber is, in atleast one segment, shaped so that in the operating position the length10 of a horizontal line 11 that divides the surface of the cross sectioninto a lower and an upper section of the surface, 20 and 21,respectively, both of which have essentially the same area, is greaterthan twice the maximum vertical extent 30 of the lower segment of thesurface 20, and/or the level of the molten glass is adjusted so that thesurface of the glass perpendicular to the direction of flow of themolten glass has a width which is more than twice as great as themaximum vertical extent of the molten glass in the refining chamber.

In another embodiment, the invention comprises a process for producing arefining chamber according to the invention, comprising: (a) inserting asmooth-walled tubular segment having two axial ends into a cylindricalmold having an inside diameter and an outside diameter, wherein thetubular segment has an inside diameter and an outside diameter, andwherein the inside diameter is essentially the same as the outsidediameter, and wherein the tubular segment has corrugation-like radialdepressions; (b) providing each of the axial ends of the tubular segmentwith a compression tool that closes the end of the tube tightly, forminga space; (c) filling the space so formed completely with a hydraulicliquid; and (d) generating an internal hydraulic pressure by exerting anaxial compression through the compression tools in such a manner thatthe walls of the tubular segment are corrugated to match the depressionsin the mold with simultaneous shortening of the tubular segment.

In another embodiment, the invention comprises using a tube according tothe invention to refine glass.

Refining chambers made of PGM materials, with a circular cross section,are known as the state of the art. In a refining chamber according tothe present invention, the width of the surface perpendicular to thedirection of flow of the glass is more than twice the depth of the glassfrom the bottom of the refining chamber to the surface. As is shownschematically in FIGS. 1(a) and 1(b), that is achieved according to theinvention by the cross section 1 of the refining chamber in theoperating position, i.e., in an essentially horizontal position, beingshaped so that the length 10 of a horizontal line 11 which divides thearea of the cross section essentially into a lower and an upper areasection 20 and 21, respectively, so that the two area sections haveessentially the same area, is greater than twice the vertical extent 30of the lower area section 20. The ratio of the length of the horizontalline to the maximum vertical extent is preferably at least 2.5:1. Inother words, if the refining chamber is filled with half the maximumpossible amount of glass, the maximum height of the glass is less thanhalf the width of the glass surface.

FIG. 2 shows examples of other possible cross sections 1 of refiningchambers according to the invention: an oval (FIG. 2(a)), a tube with aspecial cross section (“slot,” FIG. 2(b)), a (rounded) triangle (FIG.2(c)), and a (circular) polygon (FIG. 2(d)).

FIG. 3 shows a comparison of a known round cross section 1′ with anelliptical cross section 1, in which the ratio between the short andlong semiaxis of the ellipse is, for example, 1 to 2. Therefore therelation between the length 10 of the horizontal line 11 and the maximumvertical extent 30, as defined in claim 1, is 4:1. The circumferences ofthe circle and ellipse are equal to make the amount of material usedcomparable. When each is filled with the same amount of glass, thefollowing differences appear for this example embodiment: The freesurface 12′, 12 of the glass increases by 28% over the circular shape,and the maximum path 31′, 31 from the lowest point at the bottom to thesurface decreases by 34%.

Thin-walled plate structures have very little stiffness, especially athigh operating temperatures. To compensate for this disadvantage, it ispreferred either increase the thickness of the material, or stabilizethe structure by stiffening measures such as shaping of creases,corners, waves or folds.

DE-A-100 51 946 describes a process for producing tubular structuralparts from PGM materials through expansion by internal hydraulicpressure. According to the process described there, a tubular structuralpart of PGM material, with radially protruding corrugations is made byreshaping a smooth-walled tubular segment, by inserting a smooth-walledtubular segment into a cylindrical mold having an inside diameteressentially the same as the outside diameter of the tubular segment, andwhich has radial corrugation-like depressions, closing the two axialends with a compression tool, filling the space thus formed completelywith a hydraulic liquid, and then, by exerting an axial compressionthrough the compression tools, generating an internal hydraulic pressureso that the walls of the tubular segment are corrugated to match thedepressions in the mold with simultaneous shortening of the tubularsegment. The information disclosed by DE-A-100 51 946 is herebyincorporated by reference.

This process is suitable for shaping a PGM tube or a PGM tubular segmentwhich then becomes stiffer in the radial direction and more elastic inthe axial direction. In particular, this process can be used to providerefining chambers according to the present invention with stiffeningshaping measures.

While the invention has been described in connection with specificembodiments thereof, it will be understood that it is capable of furthermodifications and this application is intended to cover any variations,uses, or adaptations of the invention following, in general, theprinciples of the invention and including such departure from thepresent disclosure as come within known or customary practice within theart to which the invention pertains and as may be applied to theessential features hereinbefore set forth and as follows in the scope ofthe appended claims.

1. A refining chamber made essentially of platinum group metal materialfor glass production, comprising: a chamber in the shape of a tubehaving a cross section, wherein the cross section of the refiningchamber is, in at least one segment, shaped in the form of an ellipse oran oval so that in the operating position the length of a horizontalline that divides the surface of the cross section into a lower and anupper section of the surface, both of which have essentially the samearea, is greater than twice the maximum vertical extent of the lowersegment of the surface.
 2. The refining chamber according to claim 1,wherein the refining chamber has a wall thickness of approximately 0.5mm to 3 mm, preferably 0.7 mm to 1.5 mm, and is stiffened by shapingmeasures, said shaping measures comprising forming of creases, corners,waves, folds, or combinations thereof, at the circumference of therefining chamber.
 3. The refining chamber according to claim 1, whereinthe ratio of the length of the horizontal line to the maximum verticalextent of the lower segment of the surface is between 2.5:1 and 5:1. 4.The chamber according to claim 1, wherein the ratio of the length of thehorizontal line to the maximum vertical extent of the lower section isbetween 3:1 and 4:1.
 5. The refining chamber according to claim 1,wherein the refining chamber is essentially manufactured from an ODSmaterial and preferably a FKS 16 Pt alloy.
 6. A process for refiningglass in which the molten glass flows through a tubular refining chamberof claim 1, comprising: allowing glass in the molten state at atemperature of 1000° C. to 1700° C. to flow through the refiningchamber, wherein the cross section of the refining chamber is, in atleast one segment, shaped in the form of an ellipse or an oval so thatin the operating position, the length of a horizontal line that dividesthe surface of the cross section into a lower and an upper section ofthe surface, both of which have essentially the same area, is greaterthan twice the maximum vertical extent of the lower segment of thesurface and the level of the molten glass is adjusted in such a way thatthe surface of the glass perpendicular to the direction-of flow of themolten glass has a width which is more than twice as great as themaximum vertical extent of the molten glass in the refining chamber. 7.A process for producing the refining chamber of claim 1, comprising:inserting a smooth-walled tubular segment into a cylindrical mold havingan inside diameter essentially the same as the outside diameter of thetubular segment, and which has radial corrugation-like depressions,closing the two axial ends with a compression tool, filling the spacethus formed completely with a hydraulic liquid, and then, by exerting anaxial compression through the compression tools, generating an internalhydraulic pressure so that the walls of the tubular segment arecorrugated to match the depressions in the mold with simultaneousshortening of the tubular segment.
 8. Use of the refining chamber ofclaim 1 for refining glass.
 9. A process for producing the refiningchamber of claim 1, wherein the refining chamber is used for refiningglass.